Structural dynamics of HIV-1 TAR are modulated with small molecules. (A) TAR oscillates between a ground state (GS) and excited state (ES) characterized by base flipping and angular rearrangement of the helix. Several ligands, including argininamide and DMA-169, were shown to alter excited state accessibility, whereas other ligands such as neomycin were not. Adapted from ref. 43 with permission from Elsevier, Copyright 2020. (B) The structures of argininamide, DMA-169, and neomycin.